DFT study of the effect of L-Proline as organocatalyst on nitoaldol condensation reaction

The nitroaldol condensation reaction is one of the most synthetically useful organic reaction [1-2]. Organic catalysts such as L-proline have the ability to increase the rate of the reaction via covalent or non-covalent interactions. Theoretical studies is a powerful tool to find more details about the effect of organocatalyst on the rate and stereoselectivity of an organic reaction [4-5]. Our proposed mechanism for the nitroaldol reaction between acetone and nitromethane in the presence of L-proline as catalyst was studied by DFT methods at the B3LYP/6-31G**/PCM and M06-2X/6-31+G*/PCM levels of theory in DMSO as solvent at room temperature. The results show that the covalent interactions between the reactant and the catalyst makes the reaction path more energetic that the non-covalent one. Also, a reasonable explanation is found for the weakness of the covalent pathway to form both products of the reaction as observed in the experiments.